Two main roads lead south out of Sydney: the M5, which turns into the Hume Highway, and the Princes Highway. Both routes connect Sydney to Melbourne, but the M5/Hume Highway will get you to Melbourne in about 11 hours. The Princes Highway is a scenic coastal route that can get you to Melbourne in 2 days, though there are many attractions along the route.
The best start to your southern odyssey is a trip along the Grand Pacific Drive. This twisting touring route through the Royal National Park (south of Sydney) to the coastal town of Wollongong is being touted as New South Wales's answer to Victoria's Great Ocean Road. The scenic climax to the 169km-long (105-mile) route is the Sea Cliff Bridge, an engineering marvel that swerves out from the cliffs and soars above the pounding waves.
From Sydney, follow the Princes Highway south toward the city of Wollongong. Between the southern Sydney suburbs of Sutherland and Engadine, turn off at the sign pointing to the entrance to the Royal National Park. You will only need to pay the A$11 national park entrance fee if you intend to stop inside the park. Just driving through, or visiting the village of Bundeena, is free. There are three main turnoffs within the national park. The first takes you to the villages of Bundeena and Maianbar, with their wonderful beaches. The second takes you to Wattamolla, which has a beautiful shallow lagoon. (It takes around 3 hr. to walk from here along the cliff tops back to Bundeena.) The third turnoff takes you to Garie Beach -- a wild-looking and stunning stretch of sand with a large surf club building and great on-shore fishing. The road through the national park splits after the Garie Beach turn -- continue straight ahead. (Turn right and you'll head back to the main highway due south.)
Grand Pacific Drive then leads uphill through some magnificent stands of eucalyptus trees, before it breaks out of the forest and arrives at Bald Hill, an awe-inspiring lookout offering panoramic coastal views.
The road slowly winds its way downhill to the Sea Cliff Bridge. Stop at the northern side of the bridge (park in the village of Coal Cliff) and walk across it for some inspiring ocean views.
Grand Pacific next heads through the coastal towns of Thirroul and Austinmer, which both have nice beaches. There is a swimming pool on Austinmer beach carved out of a rock shelf and topped up by incoming tides.
The road finally winds on to Wollongong, which has a pretty harbor with fishing boats and seagulls and the like, before darting south again to Kiama.